U.S. patent application number 17/693330 was filed with the patent office on 2022-06-23 for methods for the production of cathode materials for lithium ion batteries.
The applicant listed for this patent is Ge Solartech, LLC. Invention is credited to Baoquan Huang.
Application Number | 20220199991 17/693330 |
Document ID | / |
Family ID | 1000006196844 |
Filed Date | 2022-06-23 |
United States Patent
Application |
20220199991 |
Kind Code |
A1 |
Huang; Baoquan |
June 23, 2022 |
Methods for the Production of Cathode Materials for Lithium Ion
Batteries
Abstract
The present disclosure provides methods for producing cathode
materials for lithium ion batteries. Cathode materials that contain
manganese are emphasized. Representative materials include
Li.sub.xNi.sub.1-y-zMn.sub.yCo.sub.zO.sub.2 (NMC) (where x is in
the range from 0.80 to 1.3, y is in the range from 0.01 to 0.5, and
z is in the range from 0.01 to 0.5), Li.sub.xMn.sub.2O.sub.4(LM),
and Li.sub.xNi.sub.1-yMn.sub.yO.sub.2 (LMN) (where x is in the
range from 0.8 to 1.3 and y is in the range from 0.0 to 0.8). The
process includes reactions of carboxylate precursors of nickel,
manganese, and/or cobalt and lithiation with a lithium precursor.
The carboxylate precursors are made from reactions of pure metals
or metal compounds with carboxylic acids. The manganese precursor
contains bivalent manganese and the process controls the oxidation
state of manganese to avoid formation of higher oxidation states of
manganese.
Inventors: |
Huang; Baoquan; (Troy,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ge Solartech, LLC |
Troy |
MI |
US |
|
|
Family ID: |
1000006196844 |
Appl. No.: |
17/693330 |
Filed: |
March 12, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16416236 |
May 19, 2019 |
11316157 |
|
|
17693330 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/485 20130101;
H01M 10/0525 20130101; H01M 4/525 20130101; C01D 15/02 20130101;
H01M 4/505 20130101 |
International
Class: |
H01M 4/505 20060101
H01M004/505; H01M 10/0525 20060101 H01M010/0525; H01M 4/525
20060101 H01M004/525; H01M 4/485 20060101 H01M004/485; C01D 15/02
20060101 C01D015/02 |
Goverment Interests
GOVERNMENT RIGHTS
[0002] This invention was made with government support under
Contract DE-SC0017761 awarded by the Department of Energy. The
government has certain rights in the invention.
Claims
1. A method of making a carboxylate compound comprising: reacting a
first pure metal with a first carboxylic acid in the presence of an
inorganic acid.
2. The method of claim 1, wherein said first pure metal comprises
Ni, Co, or Mn.
3. The method of claim 1, wherein said inorganic acid is selected
from the group consisting of nitric acid, hydrochloric acid,
sulfuric acid, and perchloric acid.
4. The method of claim 1, wherein said inorganic acid is nitric
acid.
5. A method of making a carboxylate compound comprising: reacting a
first metal compound with a first carboxylic acid, said reacting
including ball milling a mixture of said first metal compound and
said first carboxylic acid.
6. The method of claim 5, wherein said first metal compound is a
metal oxide or metal carbonate.
7. The method of claim 5, wherein said first metal compound
comprises Ni, Co or Mn.
8. The method of claim 5, wherein said first metal compound is
derived from a waste lithium ion battery.
Description
RELATED APPLICATION INFORMATION
[0001] This application is a divisional of and claims priority from
U.S. patent application Ser. No. 16/416,236, filed May 19, 2019,
the disclosure of which is hereby incorporated by reference.
FIELD
[0003] The present disclosure relates to cathode materials for
lithium ion batteries. More particularly, the present disclosure
relates to methods for producing transition metal oxide materials.
Most particularly, the present disclosure relates to methods for
preparing oxide materials with layers of lithium that alternate
with layers of oxides of nickel, manganese, and/or cobalt ("NMC"),
or nickel and manganese without cobalt ("NM"), or nickel, manganese
and/or cobalt and/or other elements. The materials feature a
controlled degree of mixing of transition metal cations in the
lithium layers and minimization of the presence of Mn.sup.4+ and
higher oxidation states of manganese during the synthesis.
BACKGROUND
[0004] Electric vehicles (EVs) represent safe, quick, quiet, robust
and environmentally desirable means of transportation among most
commuters. However, they account for a tiny fraction of automotive
sales, mainly because the batteries are expensive and need to be
recharged frequently. In order to meet the United States Advanced
Battery Consortium (USABC) goals for advanced batteries for EV and
facilitate more rapid market penetration of EV, the technology
requires a significantly reduced battery cost and increased
material performance.
[0005] Lithium ion batteries (LIBs) are rechargeable batteries that
generate electrical current when lithium ions shuttle to and fro
between a pair of electrodes.
LiNi.sub.1-x-yMn.sub.xCo.sub.yO.sub.2(NMC) and
LiNi.sub.1-xMn.sub.xO.sub.2 (LNM) with layered structures, and
Li.sub.xMn.sub.2O.sub.4(LM) and Li.sub.xMn.sub.2-yNi.sub.yO.sub.4
(LMN) with spinel structures, have been the major cathode
materials, while graphite has been the typical anode material. The
lithium cathode materials are responsible for about 40% of the cost
of the battery. The current manufacturing cost of NMC materials is
high due to the use of conventional hydroxide co-precipitation
method of synthesis. This multi-step process is complicated and
expensive.
[0006] Many difficult problems have been encountered in developing
next generation battery materials--in part due to an incomplete
understanding of reaction mechanisms. For example, the simple and
low-cost solid-state synthesis process has worked well for the
industrial production of LiCoO.sub.2 (LCO) and
LiNi.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2 (NCA), but has not yet
been employed in mass production of the NMC materials. Here we
briefly discuss the differences between the two materials based on
their chemistry and structure.
[0007] Although LiCoO.sub.2 has high power performance, it delivers
a low 140 mA-hr/g of storage capacity because only about half of
the Li atoms are utilized. Both LiNiO.sub.2 and LiMnO.sub.2 have
the same layered structure as LiCoO.sub.2. LiNiO.sub.2 has high
reversible capacity, but suffers from poor cycle stability and low
rate. In LiMnO.sub.2, a larger amount of Li atoms are able to
reversibly deintercalate/intercalate to the structure. However,
during cycling, the layered structure LiMnO.sub.2 tends to
transform to the cubic spinel structure LiMn.sub.2O.sub.4, leading
to significant capacity loss. A multiple cation layered structure
phase, i.e., LiNi.sub.1-x-yMn.sub.xCo.sub.yO.sub.2 (NMC), could
provide the advantages of the each of the pure cation phases while
overcoming many of the drawbacks.
[0008] In addition to crystal structure, the performance of cathode
materials for lithium batteries depends on morphology. Reducing the
particle size is critical to improving the rate performance by
shortening the lithium diffusion distance and enlarging the contact
area with the electrolyte. The use of nanostructures is an
effective way to improve the kinetics of lithium ion transport and
enhance the electrochemical performance of the cathode material.
Layered NMC nanostructures with different morphologies, such as
nanorods, porous nanorods, nanoparticles, microspheres, hollow
microspheres, and microcubes, are interesting because they display
high performance. These nanostructured materials can be synthesized
by various methods, such as hydroxide co-precipitation, carbonate
co-precipitation, combustion, solid state reaction and spray-drying
methods.
[0009] Known solid state reaction methods for the production of NMC
cathodes include reacting a mixture of cobalt-, manganese-, nickel-
and lithium-containing oxides or oxide precursors (such as the
process described in U.S. Pat. No. 7,488,465 by Eberman, entitled
"Solid state synthesis of lithium ion battery cathode material").
This production process is less efficient and high cost because it
uses expensive transition metal precursors as the starting
materials. The production of the solid state precursors is a
complicated, multistep process, which consumes a significant amount
of chemicals and energy. Furthermore, this conventional solid state
process is difficult to control.
SUMMARY
[0010] The disclosure presents methods for the production of
cathode materials for lithium ion batteries. Manganese-containing
cathode materials, such as NMC
(LiNi.sub.1-x-yMn.sub.xCo.sub.yO.sub.2), LM
(Li.sub.xMn.sub.2O.sub.4) and LNM
(Li.sub.xNi.sub.1-yMn.sub.yO.sub.2), are emphasized. These cathode
materials feature high energy density. The process comprises
reacting a mixture of nickel, manganese, cobalt, and/or lithium
precursors and calcining to form an oxide.
[0011] The precursors for nickel, manganese, and cobalt are
carboxylates. Preferred carboxylates are acetates and citrates.
Precursors for lithium include lithium hydroxide and lithium
carbonate.
[0012] The metal carboxylate precursors are prepared from metal
starting materials that enable a reduction in the cost of
production of the cathode materials. Metal starting materials
include pure metals and metal compounds. Metal compounds include
oxides, hydroxides, and carbonates.
[0013] The metal carboxylate precursors are prepared by reacting a
metal starting material with a carboxylic acid. Reactions include
liquid phase reactions and solid state reactions. Liquid phase
reactions include mixing a metal starting material with a liquid
carboxylic acid or a solution containing a carboxylic acid. Solid
phase reactions include grinding a metal starting material in the
presence of a carboxylic acid. Mixed metal precursors are prepared
by including two or more metal starting materials in the
reaction.
[0014] Metal carboxylate precursors are reacted to form an oxide
material. Reactions for forming the oxide material include liquid
phase reactions and solid state reactions. In liquid phase
reactions, liquid phase metal carboxylate precursors are combined,
stirred and heated to form a slurry. The slurry is dried, ball
milled, and calcined to form a metal oxide. A lithium precursor can
be included in the slurry before drying or added to the slurry
after drying, but before ball milling. Solid phase reactions
include ball milling solid phase metal carboxylate precursors in
the presence of a lithium precursor and then calcining to form a
metal oxide. Metal carboxylate precursors with one or a combination
of two or more metals are used in the liquid or solid phase
reactions.
[0015] The present disclosure extends to:
A method for forming an oxide material comprising: reacting a first
precursor with a second precursor, the first precursor comprising a
first compound, said first compound including a first metal bonded
to a first carboxylate group and a second carboxylate group, the
second precursor including a second compound, said second compound
including a second metal bonded to a third carboxylate group.
[0016] The present disclosure extends to:
A method of making a carboxylate compound comprising: reacting a
first pure metal with a first carboxylic acid in the presence of an
inorganic acid.
[0017] The present disclosure extends to:
A method of making a carboxylate compound comprising: reacting a
first metal compound with a first carboxylic acid, said reacting
including ball milling a mixture of said first metal compound and
said first carboxylic acid.
[0018] The present disclosure extends to:
A method for forming an oxide material comprising: reacting a first
precursor with a second precursor, the first precursor comprising a
first compound and a second compound, the first compound including
a first metal bonded to a first carboxylate group and the second
compound including the first metal bonded to a second carboxylate
group, the second precursor comprising a third compound, the third
compound including a second metal bonded to a third carboxylate
group.
[0019] The present disclosure also provides a method for directly
recycling and regenerating manganese-containing NMC, LMO and LMN
cathodes from waste lithium ion batteries, avoiding a complex
separation process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 shows XRD (X-ray diffraction) Rietveld refinement
patterns of samples of LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2 and
LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2.
[0021] FIG. 2 shows XRD (X-ray diffraction) Rietveld refinement
patterns of samples of LiNi.sub.0.7Mn.sub.0.15Co.sub.0.15O.sub.2
and LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1O.sub.2.
[0022] FIG. 3 shows SEM (Scanning Electron Microscope) images of
LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2 O.sub.2 in an as prepared
state.
[0023] FIG. 4 shows SEM (Scanning Electron Microscope) images of
LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2 after grinding.
[0024] FIG. 5 shows SEM (Scanning Electron Microscope) images of
LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2 in an as prepared
state.
[0025] FIG. 6 shows SEM (Scanning Electron Microscope) images of
LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2 after grinding.
[0026] FIG. 7 shows charge and discharge capacities of
LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2.
[0027] FIG. 8 shows rate performance of
LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2.
[0028] FIG. 9 shows charge and discharge capacities of
LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2.
[0029] FIG. 10 shows cycle performance of
LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2.
[0030] FIG. 11 shows XRD (X-ray diffraction) patterns (without
Rietveld refinement) of a sample of
LiNi.sub.0.5Mn.sub.0.2Co.sub.0.2Fe.sub.0.1O.sub.2.
[0031] FIG. 12 shows XRD (X-ray diffraction) patterns (without
Rietveld refinement) of a sample of
LiNiO.sub.0.7Mn.sub.0.3O.sub.2.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0032] The instant disclosure provides a process for producing
cathode materials for lithium ion batteries. The cathode materials
contain manganese (Mn) and are produced in high yield at low cost.
Representative cathode materials include NMC
(LiNi.sub.1-x-yMn.sub.xCo.sub.yO.sub.2), LM
(Li.sub.xMn.sub.2O.sub.4), and LNM
(Li.sub.xNi.sub.1-yMn.sub.yO.sub.2). The prevailing commercial
process for producing NMC cathodes is the hydroxide
co-precipitation process. In the state-of-the-art industrial
production method, ammonium ion is added to a solution of sulfates
of nickel, manganese, and cobalt. Nickel, manganese, and cobalt
cations form complex ions with ammonia. Caustic is then added to
induce decomposition of the transition metal ammonium complexes and
gradual precipitation of the hydroxide of NMC. Current processes
for the production of the transition metal sulfates starting
materials (MSO.sub.4) involve dissolving expensive, high grade, and
highly pure primary nickel, manganese and cobalt powders in
sulfuric acid (H.sub.2SO.sub.4). The hydroxide co-precipitation
method can produce high-density microspheres that are made of
primary crystalline nano-platelets.
[0033] The NMC hydroxide is lithiated at about 930.degree. C. in
the presence of Li.sub.2CO.sub.3. In the course of lithiation, two
protons per formula unit of the NMC hydroxide are replaced by one
lithium cation and the transition metal cations are oxidized from
bivalent (+2) to trivalent (+3). The structure change from the NMC
hydroxide to the lithiated material is very small so that the
microsphere morphology remains after calcination.
[0034] Although the lithiation process is short (usually 2-3
hours), there exists a trace amount of a higher oxidation state
manganese compound, Li.sub.2MnO.sub.3. This compound does not
contribute to reversible storage unless the voltage is raised to
over 4.5 V. In the Li--Mn--O system, Li.sub.2MnO.sub.3 is more
stable than LiMnO.sub.2 in air at high temperatures. A metastable
phase LiMnO.sub.2 can be synthesized only from lower oxidation
state manganese compounds, such as Mn(OH).sub.2 and MnCO.sub.3.
This is why NMC cathodes cannot be made by the reaction of their
corresponding oxides. Formation of Li.sub.2MnO.sub.3 depletes the
lithium content in the main NMC phase, and leads to low storage
capacity. In order to obtain a high storage capacity, a slight
excess of lithium is added to compensate for loss due to the
formation of the Li.sub.2MnO.sub.3 phase. It would be desirable to
develop a process for making NMC cathode materials that avoids
formation of the Li.sub.2MnO.sub.3 phase.
[0035] The materials obtained by the hydroxide co-precipitation
method have a highly ordered structure (low cation mixing) and are
of relatively high performance in rate capacity and kinetics.
However, the cathodes produced by this method cannot give a high
reversible capacity because nearly 50% Li cations remain in the Li
layer to stabilize the crystal structure.
[0036] With an identical layered structure, the chemical properties
of LiMO.sub.2 (M=Ni, Co, Mn) and, in particular, their transport of
lithium ions through intercalation and de-intercalation processes
are quite different. In LiMnO.sub.2, most lithium ions can be
de-intercalated because Mn.sup.4+ is quite stable in the binary
oxide MnO.sub.2. However, the layered structure of LiMnO.sub.2
tends to change to the spinel structure after most of the lithium
ions are de-intercalated. The reason is that the layered structure
of MnO.sub.2 is unstable since Van der Waals interactions of oxygen
anions between layers are too weak to hold the structure together
without Li ions. Spinel MnO.sub.2 is a three-dimensional and stable
structure because the Mn.sup.4+ ions occupy the sites of oxygen
anions alternately. In LiCoO.sub.2, only half of the lithium ions
can be de-intercalated; the other half of lithium ions remain to
stabilize the layered structure.
[0037] Compared with LiMnO.sub.2 and LiCoO.sub.2, the Ni--O bond
strength in LiNiO.sub.2 is relatively weak, especially at high
temperatures. In Ni compounds, Ni atoms have two oxidation states,
i.e., Ni.sup.3+ and Ni.sup.2+. The Ni.sup.2+ ions have a similar
size to Li.sup.+ (r.sub.Ni.sup.3+=0.056 nm, r.sub.Ni.sup.2+=0.068
nm, r.sub.Li.sup.+=0.074 nm), and situate in the Li.sup.+ ion
layers, blocking the path way of Li.sup.+ transport. This is why
LiNiO.sub.2 suffers from poor performance at high rate.
[0038] In Ni-rich materials, a replacement of a small amount of Li
by Ni in the lithium layers (weak cation mixing) gives larger
reversible capacity because excess Ni stabilizes the structure by
forming bonds between NiO.sub.2 slabs. As a result, a much higher
fraction of Li ions are able to undergo reversible
intercalation/de-intercalation. However, Ni atoms in the Li layer
can block the passage of Li.sup.+ transport, leading to poor
performance in rate capacity. Therefore, Ni.sup.2+ cations in
lithium layers should be controlled within a certain range in order
to obtain higher performance.
[0039] The term "cation mixing" is used herein to refer to the
degree to which transition metal ions enter the lithium layers of
NMC, LM, LNM, and other transition metal oxide cathode materials. A
high degree of cation mixing indicates substantial substitution of
transition metal ions in the lithium layers and greater inhibition
of lithium ion transport. A low degree of cation mixing indicates
little substitution of transition metal ion layers and a decrease
in the fraction of lithium ions available for ion transport due to
utilization of a greater fraction of lithium ions to stabilize the
structure. Cation mixing, expressed as an occupancy factor of Ni on
the Li site, can be determined by X-ray diffraction Rietveld
profile refinements. The amount of Ni cations within the Li layers
depends on the synthesis conditions.
[0040] In order to tailor the degree of cation mixing, there is a
need for a new synthetic protocol. The synthesis methods disclosed
herein enable the control of the amount of cation mixing by
programming reaction conditions. The conditions, such as
precursors, duration of ball milling, reaction temperatures and
oxygen environments, are crucial in determining crystalline phases,
morphology, and cation mixing that influence the electrochemical
performance of the NMC, LM, LNM, and related cathode materials.
[0041] The disclosure presents methods for the production of
cathode materials for lithium ion batteries. Manganese-containing
cathode materials, such as NMC
(LiNi.sub.1-x-yMn.sub.xCo.sub.yO.sub.2), LM
(Li.sub.xMn.sub.2O.sub.4) and LNM
(Li.sub.xNi.sub.1-yMn.sub.yO.sub.2), are emphasized. These cathode
materials feature high energy density. The method can also be used
generally for transition metal oxide materials. The process
comprises reacting a mixture of nickel, manganese, cobalt, and/or
lithium precursors and calcining to form an oxide.
[0042] The precursors for nickel, manganese, and cobalt are
carboxylates. Preferred carboxylates are acetates and citrates.
Other carboxylates include formate, propionate, oxalate, malonate,
isocitrate and acontitate. Carboxylates bonded to a given metal or
to multiple metals used in the preparations described herein are
the same in some embodiments and differ in other embodiments.
Precursors for lithium include lithium hydroxide and lithium
carbonate.
[0043] The metal carboxylate precursors are prepared from metal
starting materials that enable a reduction in the cost of
production of the cathode materials. Metal starting materials
include pure metals and metal compounds. Preferred starting
materials are pure metals. As used herein, "pure metal" refers to a
starting material in which the metal is present in an elemental or
zero valent state. The pure metals can be in various physical forms
(powder, flakes, particulate, nanoparticle, sheet etc.) and can be
used directly without further treatment to produce metal
carboxylate precursors that are subsequently reacted to form a
cathode material. Metal compounds include a metal in an oxidized
state (cation). Representative metal compounds include metal
oxides, metal hydroxides, and metal carbonates.
[0044] The metal carboxylate precursors are prepared by reacting a
metal starting material with a carboxylic acid. Reactions include
liquid phase reactions and solid state reactions. Liquid phase
reactions include mixing a metal starting material with a liquid
carboxylic acid or a solution containing a carboxylic acid. Solid
phase reactions include grinding a metal starting material in the
presence of a carboxylic acid. Mixed metal precursors are prepared
by including two or more metal starting materials in the
reaction.
[0045] Carboxylate ligands in the metal carboxylate precursors
include monodentate and multidentate carboxylate ligands.
Monodentate carboxylate ligands have a single carboxylate
functional group and bond to a single metal cation. Multidentate
carboxylate ligands have two or more carboxylate functional groups.
Multidentate carboxylate ligands can bond with a particular metal
cation at two or more bonding sites and/or can bond with two or
more different metal cations. Multidentate carboxylate ligands
include chelating carboxylate ligands. Acetate is an example of a
monodentate carboxylate and citrate is an example of a multidentate
carboxylate.
[0046] Metal carboxylate precursors are reacted to form an oxide
material. Reactions for forming the oxide material include liquid
phase reactions and solid state reactions. In liquid phase
reactions, liquid phase metal carboxylate precursors are combined,
stirred and heated to form a slurry. The slurry is dried, ball
milled, and calcined to form a metal oxide. A lithium precursor can
be included in the slurry before drying or added to the slurry
after drying, but before ball milling. Solid phase reactions
include ball milling solid phase metal carboxylate precursors in
the presence of a lithium precursor and then calcining to form a
metal oxide. Metal carboxylate precursors with one or a combination
of two or more metals are used in the liquid or solid phase
reactions.
[0047] In one aspect, the process utilizes manganese precursors
with bivalent manganese (Mn.sup.2+) and provides conditions that
prevent manganese from oxidizing to higher oxidation states. The
formation of byproducts, such as Li.sub.2MnO.sub.3 in which
manganese is in a high oxidation state is inhibited.
[0048] In one aspect, the process uses pure metals as starting
materials for metal precursors. Pure metals are advantageous
starting materials because they are much less expensive than the
metal sulfates used in the hydroxide co-precipitation process and
can be used without purification or preliminary processing. The
time, complexity, and energy consumption encountered in the
hydroxide co-precipitation process are avoided.
[0049] The process further provides a method to tailor the degree
of cation mixing through systematic control of reaction conditions.
Reaction conditions, such as precursor selection, duration of ball
milling, reaction temperatures and oxygen environments, are crucial
in determining the crystalline phases, product compounds, and
cation mixing that influence the electrochemical performance of
NMC, LM, LNM, and other oxide electrodes. The present process
provides great control over the structure, composition, and
oxidation states of transition metal oxide cathode materials.
Precursor Preparation
[0050] Manganese Precursors. The manganese precursors are critical
to solid-state synthesis of NMC materials because the oxidation
state of manganese needs to be low (bivalent) to prevent formation
of more highly oxidized phases that reduce storage capacity.
Carboxylate precursors are advantageous to the formation of the NMC
and other metal oxide materials because the calcination process
leads to evolution of reducing gases that act to prevent oxidation
of manganese. Manganese carboxylates, such as manganese citrate and
manganese acetate, are preferred precursors.
[0051] To prepare manganese citrate, manganese flakes and citric
acid are used as the starting materials. Manganese flakes are
crushed to small pieces and mixed with citric acid powder; then
water is gradually added at room temperature or elevated
temperatures (typically 20.degree. C.-85.degree. C.). The governing
reaction is:
3Mn+2C.sub.3H.sub.5O(COOH).sub.3.fwdarw.Mn.sub.3[C.sub.3H.sub.5O(COO).su-
b.3].sub.2+3H.sub.2 (1)
[0052] The resulting product is a slurry that can be used directly
as a metal precursor for manganese-containing oxide material as
described below. Alternatively, the slurry can be dried and used as
a metal precursor.
[0053] To prepare manganese acetate, manganese flakes and acetic
acid are used as the starting materials. Crushed manganese flakes
are loaded in a mixer, and concentrated acetic acid is gradually
added during mixing. Mixing can occur at room temperature or
elevated temperature. The governing reaction is:
Mn+2CH.sub.3(COOH).fwdarw.Mn[CH.sub.3(COO)].sub.2+H.sub.2 (2)
[0054] The resulting product is a slurry. The slurry can be used
directly or in dried form as a metal precursor for the synthesis of
manganese-containing metal oxide cathode materials.
[0055] Cobalt Precursors. Direct reaction of cobalt metal with
citric acid or acetic acid proceeds relatively slowly. In the
presence of an inorganic acid, however, cobalt metal reacts more
readily with citric acid or acetic acid to produce cobalt citrate
or cobalt acetate. As used herein, the term inorganic acid refers
to an acid that lacks carbon. Representative inorganic acids
include HNO.sub.3, HCl, H.sub.2SO.sub.4, and HClO.sub.4. When
nitric acid is used, the reactions are:
3Co+2C.sub.3H.sub.5O(COOH).sub.3/(HNO.sub.3).fwdarw.Co.sub.3[C.sub.3H.su-
b.5O(COO).sub.3].sub.2/[Co(NO.sub.3).sub.2]+3H.sub.2 (3)
Co+2CH.sub.3(COOH)/(HNO.sub.3).fwdarw.Co[CH.sub.3(COO)].sub.2/[Co(NO.sub-
.3).sub.2]+H.sub.2 (4)
[0056] The slurry product is used directly or in dried form as a
metal for cobalt-containing metal oxide materials.
[0057] The compound starting material cobalt oxide reacts with
citric acid or acetic acid to form cobalt citrate or acetate
according to the following reactions:
3CoO+2C.sub.3H.sub.5O(COOH).sub.3.fwdarw.Co.sub.3[C.sub.3H.sub.5O(COO).s-
ub.3].sub.2+3H.sub.2O (5)
CoO+2CH.sub.3(COOH).fwdarw.Co[CH.sub.3(COO)].sub.2+H.sub.2O (6)
[0058] The kinetics of the reaction of cobalt oxide with carboxylic
acids is slow because of the stability of cobalt oxides. Ball
milling aids the kinetics by reducing the particle size of cobalt
oxide starting materials and increasing mixing efficiency. Shorter
reaction times result.
[0059] Other cobalt compound starting materials for cobalt metal
precursors include CO.sub.3O.sub.4, CoO, CoCO.sub.3, and
Co(OH).sub.2.
[0060] Nickel Precursors. Nickel metal reacts weakly with
carboxylic acids. In the presence of an inorganic acid, however,
nickel metal reacts more readily with citric acid or acetic acid to
produce nickel citrate or nickel acetate. When nitric acid is used,
the reactions of nickel metal with citric acid and acetic acid
nickel citrate and nickel acetate are:
3Ni+2C.sub.3H.sub.5O(COOH).sub.3/(HNO.sub.3).fwdarw.Ni.sub.3[C.sub.3H.su-
b.5O(COO).sub.3].sub.2/[Ni(NO.sub.3).sub.2]+3H.sub.2 (7)
Ni+2CH.sub.3(COOH)/(HNO.sub.3).fwdarw.Ni[CH.sub.3(COO)].sub.2/[Ni(NO.sub-
.3).sub.2]+H.sub.2 (8)
[0061] Oxides and other compounds of nickel can also be used as
starting materials for nickel precursors. The reactions of citric
acid and acetic acid with nickel oxide are:
3NiO+2C.sub.3H.sub.5O(COOH).sub.3.fwdarw.Ni.sub.3[C.sub.3H.sub.5O(COO).s-
ub.3].sub.2+3H.sub.2O (9)
NiO+2CH.sub.3(COOH).fwdarw.Ni[CH.sub.3(COO)].sub.2+H.sub.2O
(10)
[0062] Other nickel compound starting materials include
Ni(OH).sub.2, NiCO.sub.3, and Ni.sub.1-xO. Ball milling will
facilitate the kinetics of reactions of nickel compounds with
carboxylic acids to shorten the reaction time.
[0063] Mixed Precursors. Mixed precursors include precursors that
contain two or more metals and/or two or more carboxylate groups. A
pure metal or a metal compound, for example, can be reacted with
two or more carboxylic acids (e.g. a combination of citric acid and
acetic acid) to form a mixed precursor. Similarly, two or more
metal starting materials (pure metals or metal compounds) (e.g.
pure metals or compounds of Ni and Co, Ni and Mn, or Co and Mn) can
react with a carboxylic acid (e.g. citric acid or acetic acid) to
form a mixed precursor. Also, two or more metal starting materials
(pure metals or metal compounds) can react with two or more
carboxylic acids (e.g. citric acid and acetic acid) to form a mixed
precursor.
[0064] In one aspect, a mixed precursor includes a compound that
contains two or more different metals (e.g. an acetate compound
that includes Ni and Co). In another aspect, a mixed precursor
includes a compound that contains two or more different carboxylate
groups (e.g. a nickel compound that includes acetate and citrate
groups). In still another aspect, a mixed precursor includes a
compound that contains two or more different metals and two or more
different carboxylate groups (e.g. a compound that contains nickel
and cobalt along with citrate and acetate). In further aspects, the
mixed precursor includes two or more compounds, where the number
and/or type of metal and/or carboxylate group differs in the
different compounds.
[0065] Reaction of solid phase metal precursors to form metal
oxides is a potentially facile and low-cost manufacturing
technology that has been successfully applied to industrial
production of many metal oxides. The technology is especially
applicable to the production of metal oxides having constituent
metals with stable oxidation states at the elevated temperatures
typically used for solid state synthesis. LiCoO.sub.2, for example,
has a stable+3 oxidation state for Co at high temperature and can
be readily produced in a solid state reaction from solid phase
cobalt precursors. Single phase LiCoO.sub.2 with a layered
structure can form high-density nanocrystals. Many technical
challenges, however, have remained in the preparation of
manganese-containing oxide materials by solid-state reactions.
Manganese is a difficult metal constituent to control because
manganese (1) readily transforms between any of multiple oxidation
states, (2) tends to form of multiple crystalline phases that
differ in stoichiometry, (3) is highly sensitive to reaction
conditions, and (4) frequently leads to non-uniform reaction
products. Due to a limited understanding of the reaction chemistry
of manganese, solid-state reaction technology has not yet been
effectively utilized to produce NMC and other manganese-containing
oxide materials. Examples described herein demonstrate that NMC
materials can be successfully produced by using a solid-state
process when the manganese precursors described herein are used in
the reaction.
Preparation of Transition Metal Oxides
[0066] Various reaction schemes for preparing transition metal
oxides from the metal precursors described herein are described
below. Transition metal oxides that can be prepared using the
methods described herein include
Li.sub.xNi.sub.1-y-zMn.sub.yCo.sub.zO.sub.2(NMC) (where x is in the
range from 0.80 to 1.3, y is in the range from 0.01 to 0.5, and z
is in the range from 0.01 to 0.5), Li.sub.xMn.sub.2O.sub.4(LM), and
Li.sub.xNi.sub.1-yMn.sub.yO.sub.2 (LNM) (where x is in the range
from 0.8 to 1.3 and y is in the range from 0.0 to 0.8). Although
not explicitly listed, other transition metal oxide compositions
can be similarly prepared using the methods disclosed herein.
[0067] The reaction schemes and examples described below will
emphasize NMC as an illustrative transition metal oxide material.
Analogous schemes for transition metal oxides in general are
readily recognizable and can be readily implemented by those of
ordinary skill in the art.
[0068] Reaction schemes to make NMC materials include:
[0069] Scheme I: Carboxylate precursors of manganese, nickel, and
cobalt made from pure metal starting materials are used to make
NMC. Metal carboxylate precursors include manganese citrate,
manganese acetate, nickel citrate, nickel acetate, cobalt citrate,
and cobalt acetate. In one aspect, the metal carboxylate precursors
are made from a reaction of pure metals with a carboxylic acid. In
another aspect, the metal carboxylate precursors are made from a
reaction of a metal compound with a carboxylic acid. In one aspect,
the metal carboxylate precursors include residual acid and/or an
acid bonded to or complexed with a metal. The carboxylate
precursors can be prepared separately and then combined (as
slurries and/or solids) in a reaction to form a metal oxide.
Alternatively, the starting materials for the different carboxylate
precursors can be combined and reacted to form a metal oxide, where
the carboxylate precursors form as intermediates in the reaction.
In one aspect, the reaction to form a metal oxide includes ball
milling. In another aspect, the reaction to form a metal oxide
includes calcination.
[0070] Scheme II: Carboxylate precursors of nickel and cobalt made
from metal compound starting materials and a manganese carboxylate
precursor made from pure manganese metal are used to make NMC.
Metal compound starting materials for nickel and cobalt include
oxides, carbonates, and hydroxides. Oxides are preferred metal
compound starting materials. The carboxylate precursors can be
prepared separately and then combined (as slurries and/or solids)
in a reaction to form a metal oxide. Alternatively, the starting
materials for the different carboxylate precursors can be combined
and reacted to form a metal oxide, where the carboxylate precursors
form as intermediates in the reaction. In one aspect, the reaction
to form a metal oxide includes ball milling. In another aspect, the
reaction to form a metal oxide includes calcination.
[0071] The kinetics of solid state reaction at high temperature are
closely related to the diffusion of particles. Application of heat
enhances the rate of diffusion, and thus increases the rate of the
reaction. High temperatures promote the formation of
Li.sub.2MnO.sub.3 and a high degree of cation mixing, whereas
moderate temperatures and oxidizing atmospheres favor the formation
of lower cation mixing because of the stabilization of Ni.sup.3+.
Ball milling can reduce particle size and increase the efficiency
of mixing, thus increasing kinetics.
[0072] Lithiation and Calcination: Formation of lithium cathode
materials requires lithiation of transition metal oxide compounds
made with the methods described herein. Lithiation is accomplished
with a lithium precursor. A lithium precursor is a compound that
includes lithium. Preferred lithium precursors include
Li.sub.2CO.sub.3 and LiOH.sym.OH.sub.2O. In one aspect, lithiation
is accomplished by combining one or more metal precursors with a
lithium precursor in a ball milling jar. A small amount of acetone
or other liquid may also be added as a wetting agent to the jar
because wet-milling is much more efficient than dry-milling. The
resulting mixture is slowly heated to e.g. 600-950.degree. C., and
kept at that temperature for ten to twenty hours. In one aspect,
calcination occurs in air. Representative calcination conditions
are presented in the examples below.
[0073] During the solid-state reactions that are induced by
calcination, the metal precursors decompose to form nanoparticles.
An air environment controlling condition is dependent on the
selection of the precursors. When metal carboxylate precursors are
used in the solid state reaction, decomposition releases CO,
CO.sub.2, and H.sub.2O. As noted above, residual nitrate groups are
present in some embodiments of metal carboxylate precursor and lead
to production of NO.sub.x and O.sub.2 during decomposition.
NO.sub.x and/or O.sub.2 may react with CO. The decomposition
products contain a balance of reducing and oxidizing species that
inhibit oxidation of manganese to Mn.sup.4+ or higher in the metal
oxide product while also inhibiting reduction of nickel to
Ni.sup.2+ in the metal oxide product. The presence of the preferred
oxidation states Mn.sup.3+ and Ni.sup.3+ in the metal oxide product
is increased.
[0074] For nickel-rich NMC materials, high temperatures enhance the
rate of the reaction, but increase the degree of cation mixing
whereas moderate temperatures favor the formation of an ordered
structure with less cation mixing, but this needs a prolonged
reaction time. High temperatures and prolonged reaction time
increase the formation of Li.sub.2MnO.sub.3. Citrates and acetates
increase the atomic level connections among Ni, Mn, Co and Li
cations or atoms through chelating, thereby facilitating a drastic
increase in the reaction rate. The degree of interconnectedness of
metal cations or atoms can be controlled through the ratio of
acetate and citrate groups present in the reaction mixture (or more
generally, the ratio of monodentate and multidentate groups). In
one aspect, citrate (and other multidentate carboxylate) groups are
capable of forming extending chains or networks that include
multiple metal cations or atoms to form an interconnected
structure. Acetate (and other monodentate carboxylate) groups bond
to a single metal cation or atom and act to disrupt chains or
extended networks to promote formation of a less interconnected
structure.
[0075] The ratio of multidentate carboxylate groups (e.g. citrate)
to monodentate carboxylate groups (e.g. acetate) in the reaction
mixture used to form a metal precursor, mixed metal precursor or
metal oxide is in the range from 0.25-2.0, or in the range from
0.50-1.5, or in the range from 0.7-1.3, or in the range from
0.85-1.2.
[0076] Metal citrates and acetates (and other metal carboxylates)
decompose to form nanoparticles that can enhance the rate of
diffusion. Furthermore, decomposition of carboxyl groups releases
reducing gases to protect manganese from oxidizing. In order to
avoid oxidizing manganese, the air flow rate should be controlled
during calcinations. In addition, ball milling can reduce particle
sizes, and wet milling increases the mobility of particles to
enhance mixing efficiency, thereby reducing the reaction time. The
synthesis conditions greatly affect the structures and performances
of materials.
[0077] Metal oxides prepared from the metal precursors described
herein include Li.sub.xNi.sub.1-y-zMn.sub.yCo.sub.zO.sub.2, where x
is in the range from 0.80 to 1.3, y is in the range from 0.01 to
0.5, and z is in the range from 0.01 to 0.5; and
Li.sub.xMn.sub.2O.sub.4, where x is in the range from 0.8 to 1.3;
and Li.sub.xNi.sub.1-yMn.sub.yO.sub.2, where x is in the range from
0.8 to 1.3 and y is in the range from 0.0 to 0.8.
[0078] The present invention also provides a method for directly
recovering and re-synthesizing an NMC cathode from a waste lithium
ion battery, avoiding a complex separation process. In particular,
the process uses a carboxylic acid to reduce manganese present in a
higher oxidation state (e.g. Mn.sup.4+) in the waste to generate
new cathode material with manganese present in a lower oxidation
state (e.g. Mn). In more particular, the cathode can be recovered
by sintering the waste in a reducing environment such as hydrogen
and carbon monoxide.
[0079] Example 1. Preparation of Mixed Manganese Precursor
Solution. 20.0 g crushed electrolytic Mn flakes, 20.0 g acetic acid
and 20.0 g citric acid were put in a beaker. 200 ml of distilled
water was gradually added. The mixture was heated at 95-100.degree.
C. until the Mn was completely reacted. The product was a liquid
phase mixed manganese precursor. The final weight of the Mn
precursor solution was 110.4 g (18.3 wt % Mn).
[0080] Example 2. Preparation of Nickel Acetate Precursor Solution.
394.5 g nickel balls (3-10 mm diameter), 100 ml of distilled water,
20 g aqueous HNO.sub.3 (67 wt %), 15 g acetic acid and 15 g citric
acid were placed in a PTFE beaker with a cap. The beaker was heated
at 95-100.degree. C. for five hours. While heating, an additional
200 ml of distilled water was gradually added to prevent the
reaction mixture from drying out. Partial reaction of the nickel
balls occurred during the reaction time. The unreacted portion of
the nickel balls was separated from the solution and rinsed three
times with 10 ml of distilled water. The rinse product was added
back to the solution. The unreacted nickel balls were then further
rinsed with a large amount of water and dried. The final weight of
the unreacted portion of the nickel balls was 375.3 g, which means
that the net nickel weight in the product nickel acetate precursor
solution was 17.2 g. The final weight of the nickel precursor
solution was 200.5 g (8.58 wt % of which was nickel).
[0081] Example 3. Preparation of Cobalt Acetate Precursor Solution.
209.9 g cobalt flakes, 100 ml distilled water, 17 g aqueous
HNO.sub.3 (67 wt %), and 20 g acetic acid were placed in a PTFE
beaker with a cap. The beaker was heated at 95-100.degree. C. for
five hours. While heating, an additional 200 ml distilled water was
gradually added to prevent the reaction mixture from drying out.
Partial reaction of the cobalt flakes occurred during the reaction
time. The unreacted portion of the cobalt flakes was separated from
the solution and rinsed with 10 ml distilled water. The rinse
product was added back to the solution. The unreacted cobalt flakes
were then further rinsed with a large amount of water and dried.
The final weight of the unreacted cobalt flakes was 193.1 g, which
meant that the net cobalt weight in the cobalt acetate precursor
solutions was 15.9 g. The final weight of the cobalt acetate
precursor solution was 169.9 g (9.36 wt % of which was cobalt).
[0082] Example 4. Preparation of NMC622
(LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2). 123.1 g of the nickel
acetate precursor solution (Example 2), 18.0 g of the mixed
manganese precursor solution (Example 1), and 37.8 g of the cobalt
acetate precursor solution (Example 3) were put in a beaker with a
cap. The beaker was heated at 95-100.degree. C. for 1 hour while
stirring. 14.5 g of LiOH.H.sub.2O was then added with stirring
while maintaining the temperature at 95-100.degree. C. to form a
viscous slurry. The resulting slurry was dried at 130.degree. C.
overnight. The dried slurry was placed in a one-liter jar. 1 kg of
a grinding medium (ZrO.sub.2, average particle size 3/8'') and 70 g
of acetone were added to the jar. The dried slurry was then milled
in the jar for 5 hours. The milled product was dried in air and
loaded in a Al.sub.2O.sub.3 crucible for calcination. Calcination
included increasing the temperature of the crucible from room
temperature to 950.degree. C. over a time period of 3 hours. The
crucible was then held at 950.degree. C. for 10 hours, cooled from
950.degree. C. to 600.degree. C. over a time period of 5 hours,
kept at 600.degree. C. for 5 hours, and then cooled to room
temperature over a time period of 5 hours. The final product was
ground and characterized by XRD, SEM, and electrochemical half-cell
testing.
[0083] Example 5. Preparation of a Mixed Precursor for NMC532
(LiNiI.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2). 8.8 g Ni powder (with
an average diameter of 3 .mu.m-7 .mu.m), 3.5 g Co powder (200
mesh), 4.9 g crushed Mn powder, 18.9 g citric acid and 18 g acetic
acid were placed in a beaker and mixed. The metal powders had an
average diameter of 3 .mu.m-7 .mu.m. 100 ml of aqueous HNO.sub.3
solution (7 wt %) was gradually added at room temperature and the
mixture was heated at 95-100.degree. C. for 3 hours while stirring.
During the 3-hour reaction time period, an additional 100 ml
distilled water was added to prevent the reaction mixture from
drying out. The resulting slurry was dried overnight.
[0084] Example 6. Preparation of NMC532
(LiNi.sup.0.5Mn.sub.0.3Co.sub.0.2O.sub.2). The mixed precursor for
NMC532 described in Example 5 was placed in a one-liter jar. 12.7 g
Li.sub.2CO.sub.3, 1 kg of grinding medium (ZrO.sub.2, average
particle size 3/8'') and 70 g of acetone were added to the jar. The
contents of the jar were milled for 5 hours. The milled product was
dried overnight in air and loaded in a Al.sub.2O.sub.3 crucible for
calcination. To calcine, the crucible was heated from room
temperature to 950.degree. C. over a time period of 3 hours. The
crucible was then held at 950.degree. C. for 10 hours, cooled from
950.degree. C. to 600.degree. C. over a time period of 5 hours,
kept at 600.degree. C. for 5 hours, and then cooled to room
temperature over a time period of 5 hours. The final product was
ground and characterized by XRD (FIG. 1), SEM (FIG. 3 and FIG. 4),
and electrochemical half-cell testing (FIG. 7 (charge and discharge
capacity over two cycles at 0.1C rate) and FIG. 8 (rate performance
at various rates (0.1C, 1/3C, and 1C)).
[0085] Example 7. Preparation of a Mixed Precursor for NMC701515
(LiN.sub.0.7Mn.sub.0.15Co.sub.0.15O.sub.2). 12.3 g Ni powder (with
an average diameter of 3 .mu.m-7 .mu.m), 2.7 g Co powder (200
mesh), 2.5 g crushed Mn powder, 15.0 g citric acid and 18 g acetic
acid were placed in a beaker and mixed. The metal powders had an
average diameter of 3 .mu.m-7 .mu.m. 100 ml of aqueous HNO.sub.3
solution (12 wt %) was gradually added at room temperature and the
mixture was heated at 95-100.degree. C. for 3 hours while stirring.
During the 3-hour reaction time period, an additional 120 ml
distilled water was added to prevent the reaction mixture from
drying out. The resulting slurry was dried overnight.
[0086] Example 8. Preparation of NMC701515
(LiNI.sub.0.7Mn.sub.0.15Co.sub.0.15O.sub.2). The mixed precursor
for NMC701515 described in Example 7 was placed in a one-liter jar.
12.7 g Li.sub.2CO.sub.3, 1 kg of grinding medium (ZrO.sub.2,
average particle size 3/8'') and 70 g of acetone were added to the
jar. The contents of the jar were milled for 5 hours. The milled
product was dried overnight in air and loaded in a Al.sub.2O.sub.3
crucible for calcination. To calcine, the crucible was heated from
room temperature to 93.degree. C. over a time period of 3 hours.
The crucible was then held at 930.degree. C. for 5 hours, cooled
from 930.degree. C. to 800.degree. C. over a time period of 5
hours, kept at 800.degree. C. for 30 hours, cooled from 800.degree.
C. to 750.degree. C. over a time period of 2 hours, kept at
750.degree. C. for 20 hours, cooled from 750.degree. C. to
600.degree. C. over a time period of 5 hours, kept at 600.degree.
C. for 5 hours, and then cooled to room temperature over a time
period of 5 hours. The final product was ground and characterized
by XRD (FIG. 2).
[0087] Example 9. Preparation of a Mixed Precursor for NMC811
(LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1O.sub.2). 14.1 g Ni powder (with
an average diameter of 3 .mu.m-7 .mu.m), 1.8 g Co powder (200
mesh), 1.6 g crushed Mn powder, 15.0 g citric acid and 18 g acetic
acid were placed in a beaker and mixed. The metal powders had an
average diameter of 3 .mu.m-7 .mu.m. 100 ml of aqueous HNO.sub.3
solution (12 wt %) was gradually added at room temperature and the
mixture was heated at 95-100.degree. C. for 3 hours while stirring.
During the 3-hour reaction time period, an additional 120 ml
distilled water was added to prevent the reaction mixture from
drying out. The resulting slurry was dried overnight.).
[0088] Example 10. Preparation of NMC811
(LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1O.sub.2). The mixed precursor for
NMC811 described in Example 9 was placed in a one-liter jar. 12.7 g
Li.sub.2CO.sub.3, 1 kg of grinding medium (ZrO.sub.2, average
particle size 3/8'') and 70 g of acetone were added to the jar. The
contents of the jar were milled for 5 hours. The milled product was
dried overnight in air and loaded in a Al.sub.2O.sub.3 crucible for
calcination. To calcine, the crucible was heated from room
temperature to 930.degree. C. over a time period of 3 hours. The
crucible was then held at 930.degree. C. for 5 hours, cooled from
930.degree. C. to 800.degree. C. over a time period of 5 hours,
kept at 800.degree. C. for 30 hours, cooled from 800.degree. C. to
750.degree. C. over a time period of 2 hours, kept at 750.degree.
C. for 20 hours, cooled from 750.degree. C. to 600.degree. C. over
a time period of 5 hours, kept at 600.degree. C. for 5 hours, and
then cooled to room temperature over a time period of 5 hours. The
final product was ground and characterized by XRD (FIG. 2).
[0089] Example 11. Preparation of a Mixed Manganese Precursor. 3.3
g Mn flakes were crushed and ground in a mortar. 3.6 g acetic acid
and 3.9 g citric acid were then added with mixing. 10 ml water was
gradually added during mixing to promote the reaction. The final
product was a solid phase mixed Mn precursor in the form of a
powder.
[0090] Example 12. Preparation of a Mixed Nickel-Cobalt Precursor.
13.9 g of Ni.sub.xO (76 wt % Ni), 4.5 g of CoO, 14.4 g of acetic
acid and 15.1 g of citric acid were placed in a mortar and ground
for 30 min. The mixture was transferred into a container sealed
with a cap and left overnight to dry.
[0091] Example 13. Preparation of NMC622
(LiNI.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2). The mixed manganese
precursor of Example 11, the mixed nickel-cobalt precursor of
Example 8, 12.7 g of Li.sub.2CO.sub.3, 1 kg of grinding medium
(ZrO.sub.2, average particle diameter 3/8'') and 70 g acetone were
placed in a one-liter jar and ball-milled for 5 hours. The milled
product was dried in air and loaded in a Al.sub.2O.sub.3 crucible
for calcination. To calcine, the crucible was heated from room
temperature to 950.degree. C. over a time period of 3 hours. The
crucible was then held at 950.degree. C. for 10 hours, cooled from
950.degree. C. to 600.degree. C. over a time period of 5 hours,
kept at 600.degree. C. for 5 hours, and then cooled to room
temperature over a time period of 5 hours. The final product was
ground and characterized by XRD (FIG. 1), SEM (FIG. 5 and FIG. 6),
and electrochemical half-cell testing (FIG. 9 (charge and discharge
capacity at various rates (0.1C, 1/3C, and 1C)) and FIG. 10
(charge-discharge performance over multiple cycles)).
[0092] Example 14. Preparation of
LiNi.sub.0.5Mn.sub.0.2Co.sub.0.2Fe.sub.0.1O.sub.2. This example
illustrates the versatility of the method described herein for
preparing new compositions for lithium ion cathode materials. In
particular, this example illustrates a modified form of the NMC
family of materials to include other transition metal cations.
Incorporation of Fe is illustrated, but the method applies
generally to other transition metals.
[0093] NMC materials with ferrous ion (Fe.sup.2+) are difficult to
synthesize with co-precipitation and other prior art methods
because the presence of ferrous ion promotes cation mixing. Ferrous
ion, for example, has a greater tendency to enter the planar
Li.sup.+ layer of the structure than nickel. With the present
method, NMC materials containing ferrous ion and a low degree of
cation mixing can be prepared.
[0094] Preparation of a Mixed Precursor for
LiNI.sub.0.5Mn.sub.0.2Co.sub.0.2Fe.sub.0.1O.sub.2). 8.8 g Ni powder
(with an average diameter of 3 .mu.m-7 .mu.m), 3.5 g Co powder (200
mesh), 3.3 g crushed Mn powder, 1.7 g Fe powder, 18.9 g citric acid
and 18 g acetic acid were placed in a beaker and mixed. The metal
powders had an average diameter of 3 .mu.m-7 .mu.m. 100 ml of
aqueous HNO.sub.3 solution (7 wt %) was gradually added at room
temperature and the mixture was heated at 95-100.degree. C. for 3
hours while stirring. During the 3-hour reaction time period, an
additional 100 ml distilled water was added to prevent the reaction
mixture from drying out. The resulting slurry was dried overnight.
12.7 g Li.sub.2CO.sub.3, 1 kg of grinding medium (ZrO.sub.2,
average particle size 3/8'') and 70 g of acetone were added to the
jar. The contents of the jar were milled for 5 hours. The milled
product was dried overnight in air and loaded in a Al.sub.2O.sub.3
crucible for calcination. To calcine, the crucible was heated from
room temperature to 930.degree. C. over a time period of 3 hours.
The crucible was then held at 930.degree. C. for 5 hours, cooled
from 930.degree. C. to 800.degree. C. over a time period of 5
hours, kept at 800.degree. C. for 30 hours, cooled from 800.degree.
C. to 750.degree. C. over a time period of 2 hours, kept at
750.degree. C. for 20 hours, cooled from 750.degree. C. to
600.degree. C. over a time period of 5 hours, kept at 600.degree.
C. for 5 hours, and then cooled to room temperature over a time
period of 5 hours. The final product was ground and characterized
by XRD (FIG. 11).
[0095] Example 15. Preparation of a Mixed Precursor for
LiNi.sub.0.7Mn.sub.0.3O.sub.2. 12.3 g Ni powder (with an average
diameter of 3 .mu.m-7 am), 4.9 g crushed Mn powder, 15.0 g citric
acid and 18 g acetic acid were placed in a beaker and mixed. 100 ml
of aqueous HNO.sub.3 solution (12 wt %) was gradually added at room
temperature and the mixture was heated at 95-100.degree. C. for 3
hours while stirring. During the 3-hour reaction time period, an
additional 120 ml distilled water was added to prevent the reaction
mixture from drying out. The resulting slurry was dried overnight.
12.7 g Li.sub.2CO.sub.3, 1 kg of grinding medium (ZrO.sub.2,
average particle size 3/8'') and 70 g of acetone were added to the
jar. The contents of the jar were milled for 5 hours. The milled
product was dried overnight in air and loaded in an Al.sub.2O.sub.3
crucible for calcination. To calcine, the crucible was heated from
room temperature to 950.degree. C. over a time period of 5 hours.
The crucible was then held at 950.degree. C. for 10 hours, cooled
from 950.degree. C. to 800.degree. C. over a time period of 5
hours, kept at 800.degree. C. for 30 hours, cooled from 800.degree.
C. to 750.degree. C. over a time period of 2 hours, kept at
750.degree. C. for 20 hours, cooled from 750.degree. C. to
600.degree. C. over a time period of 5 hours, kept at 600.degree.
C. for 5 hours, and then cooled to room temperature over a time
period of 5 hours. The final product was ground and characterized
by XRD (FIG. 12).
[0096] The XRD data shown in FIGS. 1, 2 and 11 indicate that the
NMC products exhibit a low degree of cation mixing. Cation mixing
can be the ratio of the intensity of the (003) diffraction peak
(I.sub.003) to the intensity of the (104) diffraction peak
(I.sub.104). The (003) and (104) diffraction peaks are labeled in
FIGS. 1, 2, and 11. As the degree of cation mixing increases, the
ratio I.sub.003/I.sub.104 decreases. A ratio I.sub.003/I.sub.104
less than 1.20 indicates a high degree of cation mixing and poor
electrochemical performance of the metal oxide when used as a
cathode material for lithium ion batteries. The I.sub.003/I.sub.104
ratios for the materials shown in FIGS. 1 and 2 are 1.38
(LiNi.sub.0.6Mn.sub.0.2Co.sub.0.2O.sub.2), 1.55
(LiNi.sub.0.8Mn.sub.0.1Co.sub.0.1O.sub.2), 1.86
(LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2), and 1.87
(LiNi.sub.0.7Mn.sub.0.15Co.sub.0.15SO.sub.2). Materials prepared by
the methods described herein have an intensity ratio
I.sub.003/I.sub.104 greater than 1.30, or greater than 1.40, or
greater than 1.50, or greater than 1.60, or greater than 1.70, or
greater than 1.80, or in the range from 1.35-1.95, or in the range
from 1.45-1.90, or in the range from 1.55-1.85.
[0097] A first aspect of the disclosure is a method for forming an
oxide material comprising:
[0098] reacting a first precursor with a second precursor, the
first precursor comprising a first compound, said first compound
including a first metal bonded to a first carboxylate group and a
second carboxylate group, the second precursor including a second
compound, said second compound including a second metal bonded to a
third carboxylate group.
[0099] A second aspect of the disclosure is the first aspect,
wherein said first carboxylate group is acetate or citrate.
[0100] A third aspect of the disclosure is the first or second
aspect, wherein said second carboxylate group is citrate or
acetate.
[0101] A fourth aspect of the disclosure is any of the first
through third aspects, wherein said third carboxylate group is
acetate, citrate, formate, propionate, oxalate, malonate,
isocitrate or acontitate.
[0102] A fifth aspect of the disclosure is any of the first through
fourth aspects, wherein said first metal is Ni or Co.
[0103] A sixth aspect of the disclosure is any of the first through
fifth aspects, wherein said second metal is Mn.
[0104] A seventh aspect of the disclosure is any of the first
through sixth aspects, wherein said third metal is Al, Fe, Cu, Zn,
Ti, or Zr.
[0105] An eighth aspect of the disclosure is any of the first
through seventh aspects, wherein said reacting occurs at a
temperature between 600 to 950.degree. C.
[0106] A ninth aspect of the disclosure is any of the first through
eighth aspects, wherein said reacting comprises ball milling a
mixture of said first precursor and said second precursor.
[0107] A tenth aspect of the disclosure is any of the first through
ninth aspects, wherein said reacting produces a product
comprising:
Li.sub.XNi.sub.1-y-zMn.sub.yCo.sub.zO.sub.2,
[0108] wherein x is in the range from 0.80 to 1.3, y is in the
range from 0.01 to 0.5, and z is in the range from 0.01 to 0.5.
[0109] An eleventh aspect of the disclosure is any of the first
through ninth aspects, wherein said reacting produces a product
comprising:
Li.sub.xMn.sub.2O.sub.4
[0110] wherein x is in the range from 0.8 to 1.3.
[0111] A twelfth aspect of the disclosure is any of the first
through ninth aspects, wherein said reacting produces a product
comprising:
Li.sub.xNi.sub.1-yMn.sub.yO.sub.2
[0112] wherein x is in the range from 0.8 to 1.3 and y is in the
range from 0.0 to 0.8.
[0113] A thirteenth aspect of the disclosure is a method of making
a carboxylate compound comprising:
[0114] reacting a first pure metal with a first carboxylic acid in
the presence of an inorganic acid.
[0115] A fourteenth aspect of the disclosure is the fourteenth
aspect, wherein said first pure metal comprises Ni, Co, or Mn.
[0116] A fifteenth aspect of the disclosure is the thirteenth or
fourteenth aspect, wherein said inorganic acid is selected from the
group consisting of nitric acid, hydrochloric acid, sulfuric acid,
and perchloric acid.
[0117] A sixteenth aspect of the disclosure is any of the
thirteenth through fifteenth aspects, wherein said inorganic acid
is nitric acid.
[0118] A seventeenth aspect of the disclosure is a method of making
a carboxylate compound comprising:
[0119] reacting a first metal compound with a first carboxylic
acid, said reacting including ball milling a mixture of said first
metal compound and said first carboxylic acid.
[0120] An eighteenth aspect of the disclosure is the seventeenth
aspect, wherein said first metal compound is a metal oxide or metal
carbonate.
[0121] A nineteenth aspect of the disclosure is the seventeenth or
eighteenth aspect, wherein said first metal compound comprises Ni,
Co or Mn.
[0122] A twentieth aspect of the disclosure is any of the
seventeenth through nineteenth aspects, wherein said first metal
compound is derived from a waste lithium ion battery.
[0123] Those skilled in the art will appreciate that the methods
and designs described above have additional applications and that
the relevant applications are not limited to those specifically
recited above. Also, the present invention may be embodied in other
specific forms without departing from the essential characteristics
as described herein. The embodiments described above are to be
considered in all respects as illustrative only and not restrictive
in any manner.
* * * * *